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January 8, 2012

ASM file number 8

The disk Used Space Directory (USD) – ASM file number 8 - maintains the number of allocation units (AU) used per zone, per disk in a disk group. The USD is split into a set of Used Space Entries (USE). Each USE will maintain a counter for the number of used AUs per disk, per zone. A disk zone can be either HOT or COLD.

This structure is version 11.2 specific and is relevant to the Intelligent Data Placement feature. The USD will be present in a newly created disk group in version 11.2 or when the ASM compatibility is advanced to 11.2.

Locating the used space directory

Let's get the allocation units for the used space directory - for all disk groups.

This action triggers the rebalance for disk group DATA, as file extents have to be moved to disks' hot regions. Once the rebalance completes, the last query shows more data in hot region for disks in disk group number 2.

The disk Used Space Directory (USD) – ASM file number 8 - maintains the number of allocation units (AU) used per zone, per disk in a disk group. It is a supporting metadata structure for the Intelligent Data Placement feature in ASM version 11.2. One handy use of this feature is a control of datafile placement in disks' hot or cold zones.

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As a child, I wanted to be a pilot; but it's not so exciting when
your in-flight movie is the sky. As a teenager, I wanted to be an
artist; but I prefer having an income. As an adult, I had my mind set on
becoming a scientist. I slaved away studying mathematics and digital
electronics, in the vain hopes of becoming the next Tesla, sitting in my workshop surrounded by thousands of volts. But it was not to be. My heart lies
with computers: taking them apart, putting them together, and forcing them to do my bidding.

My love for technology has taken me around the
world. In Serbia, I designed motherboard clock circuitry; in England, I
put together custom PCs; and in Australia, I wrote a program to control
the AC fans in Melbourne's tallest building. Many a lazy summer day was
spent turning off the cooling on the top floor, to the chagrin of my
coworkers. Today, I have cleaned up my act, and work as a support guy at
Oracle.